The kinetochore is a control module that both powers and
regulates chromosome segregation in mitosis and meiosis.
The kinetochore-microtubule interface is remarkably fluid,
with the microtubules growing and shrinking at their point
of attachment to the kinetochore. Furthermore, the
kinetochore itself is highly dynamic, its makeup changing
as cells enter mitosis and as it encounters microtubules.
Active kinetochores have yet to be isolated or reconstituted,
and so the structure remains enigmatic. Nonetheless, recent
advances in genetic, bioinformatic and imaging technology
mean we are now beginning to understand how
kinetochores assemble, bind to microtubules and release
them when the connections made are inappropriate, and
also how they influence microtubule behaviour. Recent
work has begun to elucidate a pathway of kinetochore
assembly in animal cells; the work has revealed that many
kinetochore components are highly dynamic and that
some cycle between kinetochores and spindle poles along
microtubules. Further studies of the kinetochoremicrotubule
interface are illuminating: (1) the role of
the Ndc80 complex and components of the Ran-GTPase
system in microtubule attachment, force generation and
microtubule-dependent inactivation of kinetochore spindle
checkpoint activity; (2) the role of chromosomal passenger
proteins in the correction of kinetochore attachment
errors; and (3) the function of microtubule plus-end
tracking proteins, motor depolymerases and other proteins
in kinetochore movement on microtubules and movement
coupled to microtubule poleward flux.